Tension pulley



P. G. PALMGREN ET AL 2,541,278

TENSION PULLEY Filed Jan. 16, 1947 Patented Feb. 13, 1.951

UNITED lsl'rll-'lss/ ors-lic E1;

tewartV Murray; Norristown, Fats,1 assignorsrttr SKF Industries;Inc.,/,Philadeiphi'a:;ela:., a cursw porationofinelawareAppii'eatibnnnuary 1s, 194:1; sedermi.- 722.4161:

vf claim-Si (ci. 'rs-zanzara This inventionn relates to improvementsinf-teni-V sion pulleys' for tape", band or belt drives intox-- tileYmachines, and to thermounting of such pulleys in brackets attacheditothe machines.

A principal object of this invention is to provide a" mounting for theIpulley assembly that will rendersaid assembly readily adaptable tobraak'- etsialread'y' in use forplainbearingsand will permit quickinstallation in such brackets.

Anotherobject is to providea pulley having relatively low windageresistance.

Another object` is to provide pulley parts' that. will' notY c'orrode intheY relatively moist' atmosphere of textile mills.

StillV another object is to provide aA pulley that will not,ily/sparking, set fire to the lint andI dust prevalent in the air'oftextileY mills;

A further Objectis to` produce a pulley having excellent' dynamicbalance at low cost.

Other objects Willappear from a consideration ofthe following`description and of the attacheddrawings, wherein:

Fig. 1 is a front elevational and partial 'sectional'.' View of` pulleyassembly made in accordance. with theV invention;

Fig. 2- is a side elevational View' of the assembly; and

Figs. 3 and 4 are views in perspective of two' different, elements ofthe assembly.

Tension pulleys'l of the type involved convent'ionall'yv hang in.brackets attached toVv arms which' swing aroundstuds fixed tothe'frameof the`textile machine.. An overbalancedWeightfastenedv tothearm. causes the pulley Vto press against thel tape, belt` or band whichdrives44 one or` more spindles ofthe machine, and thereby imparts auniform tensiony throughout such belt or band. Such pulleys may turn at,say, two to ve thou-v sand` revolutions per minute and thus require'kcareful consideration with respect to'several features in order thattheyI may performtheir functions with the leastv disturbanceI to therunning cli" the tape andv wih he least consumption of power. First,theA pulley should possess` good dynamic bal'ance'so that it mayr runsteadily'and avoid" any swingingA of the arm which wouldv causewhipping' of the tape; second, it should operate with low frictionto'reduce power loss third, it should not' corrodein the moist'atmosphere of the mills wherein such condition is often artificiallyproduced; fourth, it should produce no staticr electrical charges thatcould result in s; spark that might` set ilretothe fine lintand `dustwhich pervades the air of such mills; and" ilfth, theV pulley vsurfaceshould remain' free from oil;v greasefor anyi'iiliir of lubricantfstrayingfromthe bearingchamber:

We have" achieved all off these, .and other" desirable properties.inlthe pull'eybyA the organization of.: elements 'hereinafter described;

The invention consists' of a` pulley I; which preferably made ofplastic` material molded to" precise dim'ensi'onsinv a'- completelyfinished state.. The, plasticizmaterialpreferred'for this pulley isVonek that will" finish close to: the dimensionsv requiredforspropen Ilt; of-the anti-friction bearing upon which itr is tok bemountedg thuseliminating; necessity for.' anyjfinishingv process such, as grinding;to.v bring; itto size. 'The outer race. of theisai'd bearingzmustgo intothe pulley hub' v2 witha press ilt sufli'cintlto hold it iirmly without.eliminating entirely the internal looseness of" the bearing. byreduction. ofi` the outer ring size. Wehavev foundtl'lat in general,plastic materiallrequires ve to tenA timesas. Ymuch interferencebetweenthe bore of the..,hubf and the outside diameterpof'the bearingasdoes'a castiron orsteel housingito: producexinternal"tlconditions in;the. bearing in. accordance with correct practice. Thepulley'ihereforeturns with the outer race' 3" off the anti-frictionbearing, 42;. shown in ther drawingsas. a ball'. bearing,..sai`df. racebeing 'xedl in, ther hub 2" integralA wltlikthe sidewall 5. The. bearinghasagsiealinggplte lion,` the side opposite the sidewall'. 5v of thepi'llley,andthe said plate and" sidewali form. in effect an enclosedchamber. for. holding. grease which may be replenishedlthrough,Smallhols. T and 8', the hole 1.; being. in the pulleywall, and; thehole 8 in a cover. plate. Ill hereinafter described..

The inner race S ofthe-bearing. 4 is mounted on a shaft IU with a presst., Theoutboard ends of thefshaft. tintoLround holes Il. in rectangularblocks. Z oifwoodgplastiqor any other suitable material.. The, blocksint urn.rest.l'oosely within rectangular boxes.. leachopenon. one sideand on one end; 'Ifwo steel, springs I4. holdv the blocks nplace. byvpressingagaihst one. side; said springs beingretainedin. position. bynotches I5'. The blocks.' may be. removedby` swinging; the" springsautroflthef-notches to onefsideasrshown in; dotted lines.

Supportbracket lilshown inlthe' drawingl but not described indetail'iszof"thetypei conventionallyused in textile machinery.conventionally, al'so the pulley is' made: ofinetal v and. is secureddirectly tothe shafty l 0i Insuch conventional install'ationsv theblocks r2" areaformed'of'wood impregnated with oil.y and. thea shaft'rests.. in the round holes with'a slight clearanceand operates' as ajournal without further lubrication than that supplied by the oil soakedfibres of the wood. Because of the relatively high torque of this typeof bearing and because its exposed surfaces set in motion a materialvolume of air, power consumption is relatively high. Though small inamount in each pulley, the windage loss becomes important whenmultiplied bythe thousands of pulleys in operation throughout a givenmill. The present invention minimizes these two frictional losses byreplacing the plain high torque bearingv with an anti-friction bearingproperly lubricated and by employing plates I1, I1 which enclose allrotating surfaces of the bearing and pulley except the outer rim, thusreducing windage loss to a minimum. The plates Il, I 'I are mounted onthe shaft IU, as shown, and are normally stationary. It will be noted,however, that the plate which contains the hole 8 may be adjusted aboutthe shaft so as to bring said hole into line with the hole 1, for thepurpose of introducing lubricant as described, and so as to shift thehole 3 into an alternative position wherein it lies behind and, ineffect, is sealed by a corner of the element I8 of a member IBhereinafter described or, in the absence of such member, by a corner ofthe adjoining block I2.

It has been proposed to replace the relatively undesirable plainbearing, but heretofore such proposals have involved the eliminationalso of the aforesaid rectangular plain bearing blocks I2 and theemployment of brackets lacking the rectangular boxes I3 whichaccommodated said blocks. In the present invention we have achievedready application of the improved pulley assembly to brackets of theconventional form now in substantially universal use. This we haveaccomplished bythe novel device of inserting the shaft into the holes ofthe blocks with a t tight enough to iix'it against rotation and bymounting the anti-friction bearing on that shaft. The blocks are fittedsnugly to the pockets in rder to preclude shaking of the pulley andpreferably a rib I2a is provided on one face of the block,

i. e., the outer face, which is engaged by the springs I4, to indicatethe proper position in which the blocks Should be inserted for closestfit.

We avoid corrosion onv the moving parts by the use of plastic materialfor the pulley, and on the exposed stationary parts by making the platesof f non-corrosive material such as aluminum, plastic or stainlesssteel. Corrosion tends to hinder smooth operation, to collect lint onthe surfaces, hinder cleaning processes, and to wear out and thusshorten the lifeof theY tape belt or band,

and, if excessive, will destroy the usefulness of the pulley. Itseffective elimination is therefore an important factor.

Danger of sparking due to accumulation of static is avoided by employingan L-shaped strip, I8, of metal shown in Fig. 4. One leg I3 of thisangular strip is provided with an opening 2'0 for reception ofthe shaftlI0 and, as shown in Fig. 2, this leg I9 is confined Lbetweenthe innerend of one of the blocks I2 and the proximate face of the adjoiningplate II andin contact with the latter. The other leg 2I ofthe strip I8lies between the block and the proximate face of the bracket I6 so thatthe pulley I is in effect grounded to the bracket.

We have achieved good dynamic balance without finishing processes, byemploying a plastic, such as flock-.filled phenolic plastic, that moldsto size controllable to a dimensional accuracyA of about .001 of an inchper inch of diameter. The

saving of all finish processing reduces cost to a' minimum figure,considerably below the cost of corresponding parts made of metal.

While we prefer the above described construction because of its low costand efiiciency, certain changes may be made within the scope of theinvention, such, for example, as grinding a groove in the shaft toaccommodate the balls of the bearing, thereby eliminating requirement,of a separate inner race.

We claim:

l. In a pulley assembly, a bracket having bifurcations affordingtherebetween a space for said pulley and each containing a lateralrecess open at its inner end to said space, a relatively fixed shaftintersecting said space and extending at the ends into the respectiverecesses, stationary means confined in said recesses and anchoring thesaid ends of the shaft in the bracket, a pulley mounted for rotationabout the shaft within said space, and anti-friction bearing meansinterposed between the pulley and the shaft.

2, A pulley assembly according to claim 1 wherein the said stationarymeans are composed of nonmetallic material, and wherein further means isprovided for grounding the pulley to the bracket.

3. A pulley assembly according to claim` l wherein the said stationarymeans are composed of nonmetallic material, and wherein further ametallic strip is confined by the stationary means in one of saidrecesses in contact with the shaft and the bracket to form anelectrically conductive path therebetween.

4. In a pulley assembly, a relatively fixed shaft, a pulley mounted forrotation about the shaft, said pulley having a radial flange extendingin proximity to the shaft and an axial recess terminating at its innerend in said flange, an antifriction bearing housed in said recess andsupporting the pulley on the shaft, a disc at each axial side of thepulley secured to the shaft and extending outwardly into proximity tothe periphery of the pulley to form stationary face plates for thelatter, and aligned perforations in the said radial flange and theadjoining faceplate to afford access to the bearing for introduction ofa lubricant.

5. In a pulley assembly, a stationary shaft,.a pulley journaled on theshaft, an vanti-friction bearing interposed between the pulley and theshaft, a plate mounted on the shaft atone side of and in proximity tothe pulley and forming in effect a facing for the latter, said platebeing normally stationary and being adjustable about the shaft, astationary member adjoining the outer face of said plate, and anaperture in the plate normally lying behind and being closed `by saidstationary member, said aperture being mvable by rotative adjustment ofthe plate to an exposed position clear of said member to afford accesstherethrough to the said bearing for application to the latter of alubricating medium.

6. A pulley assembly according to claim 5 wherein the bearing is locatedin a transverse recess in the pulley, and wherein further the portion ofthe pulley which forms the bottom wallof the recess is provided with anaperture arranged for registration with the aperture in the face platewhen the latter aperture is in the exposed and operative position.

7. In a pulley assembly, a relatively fixed shaft, a pulley mounted forrotation about the shaft. said pulley having an axial recess and a wallclosing one side of said recess, a disc securedto 9,541,278 5 6 theshaft and confronting the open side of the REFERENCES CITED recess, a.second disc secured to the shaft confronting the outer face of the wallat the closed me of this patent. j side of the recess and enclosing anarrow space The following references are off-record in the betweenitself and said wall so as torestrict to a 5 UNITED STATES PATENTS smallamount the volume of air frictonally moved Number Name Date by operationof the pulley, both of said discs ex- 424,101 Dodge yMar. 25, 1890tending outwardly into proximity to the periphery 1,384,340 StegemanOct. 25, 1932 of the pulley so as to form stationary 'facing 2,204,034Hughes v.Tune 11, 1940 Plates fOr the lattel- 10 2,417,079 KavanaughMar. 11, 1947 PER GUNNAR PALMGREN. l

ALFRED STEWART MURRAY.

